RAID (Redundant Arrays of Inexpensive Disks) devices have been known as a storage device that handles plural HDDs (Hard Disk Drives) as a single logical volume.
In recent years, RAID devices have been used in places such as banks, hospitals, universities, and research centers where a large volume of information is handled, and security enhancement has been sought by using encryption functions of HDDs as measures to prevent leakage of important information.
As an encryption function of HDDs, a technology to encrypt data written in an HDD under an SED (Self-Encryption Drive) control has been known.
The SED can provide security to data written in media by means of an HDD itself encrypting the data on the media. The SED can also provide security to data accesses by password authentication.
In the SED, a unit of logical storage regions on HDDs is referred to as a band, and disk management is carried out in units of bands. A band is determined as an arbitrary range of an LBA (Logical Block Address) in HDDs.
In the technology of HDD encryption by SED control, storage systems that carry out password authentication in units of bands have been known.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2002-229859    Patent Document 2: Japanese Laid-Open Patent Publication No. 2005-202476    Patent Document 3: Japanese Laid-Open Patent Publication No. 2008-282440
However, if a third party obtains a password for a band at the time of accessing data in the SED, the third party may be able to obtain information in the HDD. Because the recent RAID devices are often used for storing personal information or research results in the banks and research centers, leakage of the important information causes tremendous damage.